JP5684852B2 - Production of shell catalyst in coating equipment - Google Patents

Description

The present invention relates to a method for producing a shell catalyst suitable for the synthesis of carboxylic acid alkenyl esters, particularly for the production of vinyl acetate monomer (VAM) from allyl acetate and ethylene obtained from propylene by an oxyacetylation method.
The present invention also provides a shell catalyst that can be obtained by the method based on the invention, and a shell catalyst or carboxylic acid alkenyl ester prepared by using the method based on the invention, particularly VAM and allyl acetate monomer. For the use of a shell catalyst according to the invention.

Supported catalysts containing palladium and gold are already known.
VAM is usually produced from a reaction mixture of ethylene, oxygen and acetic acid in the presence of a catalyst containing palladium and gold. Various production methods for such supported catalysts are already known.
By way of example, the application of a precursor compound containing the corresponding metal to the support surface, preferably dissolved in an aqueous solution.
At this time, the carrier containing the corresponding precursor compound is usually fired in an oxidizing atmosphere in a high-temperature oven, where the precursor compound containing the metal is converted into a metal oxide.
And the support | carrier containing a metal oxide is given the reduction | restoration to a metal.
In some known methods, the precursor compound need not be utilized for oxidation to metal oxide and the reduction step can be performed directly after drying.

Vinyl acetate monomer is an important component in the production of polyvinyl acetate, vinyl acetate copolymers (such as ethylene-vinyl acetate, ethylene-vinyl alcohol copolymers, etc.) and polyvinyl alcohol.
For example, VAM and the selectivity of catalysts for their production because of the widespread use of these polymers as binders in the construction, paint and varnish sectors, and as raw materials in the adhesive, paper and textile industries There is a high demand for continuous improvement of activity.

Usually, in the synthesis of VAM, a shell catalyst in which elements of palladium and gold are arranged on the outer shell of a catalyst carrier (hereinafter also referred to as “support” or “molded body”) is used. For these productions, a mixed solution of a palladium precursor compound and a gold precursor compound is usually applied to a carrier with a coating apparatus.
Then, the carrier is dried by a drying device. And the metal component of the said precursor compound changes to a metal in a reduction furnace.

  Thereafter, the reduced support is usually subjected to wet chemical impregnation with potassium acetate. In these latest methods, since the carrier is introduced into and taken out of the apparatus for various manufacturing processes, time consumption and pretreatment costs are very high.

Costs are also associated with much time consumption.
In addition, the transition between processes carried out in various devices gives the carrier mechanical stress that causes significant wear.

On the other hand, this large friction can lead to clogging of the pores of the carrier due to the formation of dust, while on the other hand, it can cause wear of the catalytically active shell with high-cost precious metals. .
In addition, there is a constant need to optimize the economic efficiency of VAM production processes using improved catalysts, due to capital consolidation of VAM and allyl acetate production plants, and particularly high raw material costs of ethylene and propylene. Has been.

Furthermore, all conventional processes for the production of vinyl acetate and allyl acetate catalysts have proven to be improved with respect to precious metal yields.
The proportion of the precious metal, palladium or gold, that ultimately remains in the catalyst during the subsequent manufacturing process and the proportion of the precious metal used is taken into account as the yield of the precious metal.
The catalyst intermediate product already covered by the noble metal is subjected to further manufacturing steps such as chemical fixation, washing, reduction and final application of alkali acetate.
Each subsequent manufacturing step and its handling in the different containers and units required will result in precious metal loss.

Accordingly, an object of the present invention is to provide a method for producing a shell catalyst that can make the production of a catalyst more effective in terms of pretreatment and time cost-effectively.
In addition, its purpose is during the manufacture of VAM shell catalysts (hereinafter “VAM” means not only “vinyl acetate monomer” but also “allylic acetate monomer”). It is to reduce the loss of precious metals.
Furthermore, the object is to provide a shell catalyst that is superior to previous catalysts in terms of selectivity and activity in the synthesis of carboxylic acid alkenyl esters.

These objects are achieved by the process according to the invention for the production of a shell catalyst characterized by the following steps:

(A) introducing a carrier into the coating apparatus;
(B) In the coating apparatus, a palladium precursor compound and a gold precursor compound are applied to the carrier by spray coating in a solution state, respectively.
(C) drying the carrier coated with the precursor compound in the coating apparatus;
(D) reducing the metal component of the precursor compound to metal in the coating apparatus; and
(E) Remove the carrier from the coating apparatus.

  When all the steps from (b) to (d) are performed in one apparatus, the production time of the catalyst is remarkably reduced, and it is necessary to transfer to another drying apparatus and a reducing apparatus. Precious metal loss can be greatly reduced because metal wear and friction problems do not occur in the carrier.

  The term shell catalyst refers to a catalyst composed of a shell with a material having catalytic activity and a support, which can be formed by two different methods.

  First, a catalytically active material is present on the outer periphery of the support, so that the support acts as a matrix of the catalytically active material and the area of the support impregnated with the catalytically active material is not impregnated A shell is formed around the center of the carrier.

Second, a new layer in which the catalyst activator is present is coated on the surface of the support.
This layer forms a new material layer which is formed as a shell around the support.
In the latter variant, the support material is not a constituent of the shell, but the shell is constituted by the catalytically active material itself or a matrix material containing a catalytically active agent material.
In the present invention, the shell catalyst of the first modification is suitable.

In the production of the shell catalyst by the method of the present invention, the metal may be present as a single atom or as an aggregate.
They preferably form aggregates.
Aggregates of a single atom or a plurality of atoms are mostly uniformly dispersed in the shell of the shell catalyst.
An aggregate of a plurality of atoms means a cluster of several metal atoms for forming a composite material existing between a single atom and a metal state (alloy).
This term includes so-called metal clusters.

  The shell thickness of the outer shell of the carrier is preferably 1 to 50%, more preferably 2 to 40%, still more preferably 3 to 30% with respect to the half thickness of the carrier, Most preferably, it is 4 to 20%.

  This percentage relates to half of the total thickness and is also related to the shape of the carrier in production, for example in spray impregnation with a solution containing the precursor compound, the precursor compound penetrates the carrier material from two outer surfaces (spherical), If the carrier material has a more complex shape, for example a cylinder, there are an inner surface and an outer surface impregnated with the precursor compound.

For carrier materials that deviate from this spherical geometry, the total thickness of the carrier is measured along the longest axis of the carrier.
The shell outer boundary is equal to the outer boundary of the metal-containing support.
The inner shell boundary means the boundary of the metal-containing carrier present in the carrier and is separated from the outer shell boundary to contain 95% by mass of all metals contained in the outer shell of the carrier. It is a point.
The shell thickness preferably does not exceed 50%, more preferably does not exceed 40%, more preferably does not exceed 30%, and most preferably does not exceed 20% for half the total thickness of the carrier.

  The metal-impregnated support preferably does not contain more than 5% of the total metal in its inner region, ie the region separated from the outside by the shell inner boundary of the metal shell.

  With regard to the shell thickness of the catalyst, it is preferred that the maximum metal concentration be located in the outer shell, for example, at the outer edge of the outer shell, close to the geometric surface of the catalyst.

The carrier is preferably composed of an inert material.
It may or may not be porous.
However, the carrier is preferably porous.
The carrier is preferably composed of regular or amorphous particles, for example, spherical, flat, columnar, cylindrical, ring-shaped, star-shaped, and its diameter, length, width is 1 to 10 mm, preferably 3 to 9 mm.

Spherical, for example, spherical particles having a diameter of 3 to 8 mm are preferred in the present invention.
The carrier can be composed of any porous and non-porous substrate, but is preferably composed of a porous substrate.
Examples of such materials include nanomaterials such as titanium oxide, silicon oxide, aluminum oxide, zircon oxide, magnesium oxide, silicon carbide, magnesium silicate, zinc oxide, zeolite, plate silicate, carbon nanotubes and carbon nanofibers. Is mentioned.

The oxide-based support material is used in the form of a mixed oxide or a specified compound, and may be, for example, TiO ₂ , SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO, SiC, ZnO or the like.
In addition, soot, ethylene black, charcoal, graphite, hydrotalcite and what are known to those skilled in the art as carrier materials can be used in different cases where improvements can be made.
The support material can preferably be doped with, for example, alkali metals or alkaline earth metals, or phosphates, halogen salts and / or sulfates.
The support preferably contains a silicon / aluminum mixed oxide or consists only of a silicon / aluminum mixed oxide.
The carrier is preferably a silicon / aluminum mixed oxide and is preferably doped with Zr at a ratio of 5 to 30% by mass with respect to the mass of the carrier.

BET surface area of the support coating is not the be in a precursor compound, at 1 to 1,000 m ² / g, is preferably 10~600m ² / g, more preferably 20 to 400 m ² / g, 80 to Particularly preferred is 170 m ² / g.
This BET surface area is defined by the 1-point nitrogen adsorption method of DIN 66132.

  In addition, the total pore volume (as defined by DIN 66133 mercury porosimeter) of the carrier not coated with the precursor compound is preferably greater than 0.1 ml / g and greater than 0.18 ml / g.

The carrier is usually produced by imposing a batch process on the majority of the carrier, and in each step a relatively high mechanical stress is imposed, for example, using stirring and mixing tools.
In addition, the shell catalyst produced by the process of the present invention is subject to strong mechanical load stresses while being charged to the reactor, especially unwanted dust formation and support damage on the outside with the catalytically active shell. May occur.

In particular, in order to keep the wear of the catalyst produced by the method of the present invention within an allowable limit, the shell catalyst has a hardness of 20N or more, preferably a hardness of 25N or more, and a hardness of 35N or more. More preferably, it has the hardness of 40N or more.
This hardness means that which is confirmed by a tablet hardness meter 8M of Dr. Schleuniger Pharmatron AG, and is determined by an average value of 99 shell catalysts under the following apparatus setting conditions after drying at 130 ° C. for 2 hours.

Distance from molded body: 5.00 mm
Time delay: 0.80s
Feed type: 6B
Speed: 0.60mm / s

The hardness of the catalyst produced by the method of the present invention can be affected, for example, by variations in limited parameters in the carrier production method, such as the calcination time and / or calcination temperature of the carrier.
The calcination is not calcination of the carrier impregnated with the metal-containing precursor compound, but merely calcination in the carrier production process before the precursor compound is applied.

Also, it is preferred that the support is 80%, preferably at least 85%, more preferably at least 90% of the total pore volume is mesopores and macropores.
This acts in the catalyst produced by the method of the present invention, in particular when the metal-containing shell has a relatively large thickness, and acts to suppress the influence due to the suppression of diffusion and the decrease in activity. Micropore, mesopore and macropore mean a diameter smaller than 2 nm, a diameter of 2 to 5 nm, and a diameter of 50 nm or more, respectively.

The activity of the shell catalyst produced by the process of the present invention is usually based on the amount of metal added to the shell.
Usually, the activity is higher when there is more metal in the shell. Here, the thickness of the shell has a relatively small influence on the activity, and is appropriately determined depending on the selectivity of the catalyst.

For the same amount of metal addition to the catalyst support, reducing the thickness of the outer shell of the catalyst usually results in higher selectivity of the catalyst produced by the process of the present invention.
In order to have a higher activity potential and to ensure a higher selectivity possibility, the optimum metal loading for the shell thickness is determined. The shell of the shell catalyst produced by the method of the present invention preferably has a thickness of 20 μm to 1000 μm, more preferably 30 μm to 800 μm, still more preferably 50 μm to 500 μm, and most preferably 100 μm to 300 μm. .

Shell thickness can be measured visually with a microscope. The portion where the metal is deposited appears black, and the region where no precious metal is present appears white. Usually, in the case of the catalyst produced according to the present invention, the boundary between the region containing noble metals and the region not containing them is sharp and can be clearly identified visually.
If the boundary is not sharp and not clearly visible, the shell thickness is deposited on the support, starting from the outer surface of the catalyst support, as already indicated. The thickness is up to 95% of the precious metal.

  In order to ensure that the homogeneous activity of the catalyst produced by the process of the present invention is generally uniform over the thickness of the noble metal-containing shell, the noble metal concentration over the shell thickness should be a relatively small change.

The characteristic of the noble metal concentration of the catalyst in the region of 90% of the shell thickness, which is 5% of the shell thickness away from the outer edge and the inner edge of the shell, is preferably such that the change from the average noble metal concentration in the region is a maximum of ± 20%. The maximum is preferably ± 15%, and if possible, the maximum is ± 10%.
Such properties are achieved, for example, by physical deposition methods such as spray coating with a solution containing the precursor compound on a carrier that is circulated in the gas.

Here, the carrier can be any device in which the carrier can be swung in a gas glide layer, but is preferably arranged in a so-called fluidized bed or fluidized bed.
The characteristics of the shell as described above are particularly preferably obtained by a fluidized bed, a fluidized bed, or a spray coating method in an Innojet AirCoater described later.

In the case of the catalyst produced according to the present invention, the dispersion of the added metal is indicated by a rectangular function where the concentration does not decrease or only slightly decreases into the support and ends at a relatively sharp boundary. Preferably (see dispersion parameters above).
In addition to this rectangular function, the addition of metal in the shell may be indicated by a triangular or trapezoidal function in which the metal concentration gradually decreases from the outside to the inside of the shell.
However, the metal dispersion is particularly preferably a rectangular function.

In step (a) in the method of the present invention, the carrier is first introduced into the coating apparatus.
In the method of the present invention, from step (a) to step (e), the carrier is not moved from the coating apparatus, and everything from step (b) to step (d) is performed in this coating apparatus. It is a feature.
This has the advantage that all travel steps are performed in one device, making this method time and cost effective and reducing metal wear.

The coating apparatus is preferably an apparatus in which the support can be swirled in the process gas glide layer and a solution of the components can be sprayed in step (b) in the method of the invention.
In addition, the apparatus preferably includes a process gas or removal gas supply port and a heating mechanism.
In a preferred form, the coating apparatus comprises a conventional coating drum, fluidized bed mechanism, or fluidized bed.

Conventional coating drums, fluidized beds, or fluidized beds suitable for the application of precursor compounds in the process of the present invention are known in the prior art, for example, Heinrich Brooks GmbH (Alfeld, Germany), ERWEKA GmbH. (Heusenstamm, Germany), Stechel (Germany), DRIAM Angelbau GmbH (Eriskirch, Germany), Glatt GmbH (Binzen, Germany), G.M. S. Division Verniciatura (Osteria, Italy), HOFER-Pharmacia Machine GmbH (Weil am Rhein, Germany), L. B. Bohle Machinen und Verfahren GmbH (Enningerloh, Germany), Lodige (o is omitted from umlauts) Machinenbau GmbH (Paderborn, Germany), Manesty Bubendorf, Switzerland), GEA Process Engineering (Hampshire, Great Britain), Fluid Air Inc. (Aurora, Illinois, USA), Heinen Systems GmbH (Varell, Germany), Hutlin (u omits umlauts) GmbH (Steinen, Germany), Uman Pharmatech Pvt. Ltd .. (Maharashtra, India) and Innojet Technologies (Lorrach (o is abbreviated umlaut), Germany).
In particular, a fluidized bed apparatus sold by Innojet Technologies, Inc., a trade name “Innojet (registered trademark) Aircoater” and a trade name “Innojet (registered trademark) Ventilus” are preferable. Here, “IAC-5 coater”, “IAC-150 coater”, or “IAC-025 coater” (all from Innojet) are particularly preferably used.

After introducing the carrier into the coating apparatus, it is preferable to first remove dust by swirling the floor with the carrier through the process gas, and the carrier is preferably held in the air glide layer by the process gas.
This step is preferably carried out at a temperature in the range of 20-50 ° C.
The removal of dust is preferably continued for 1 to 15 minutes.

  In the method of the present invention, it is preferable that in the step (b), the palladium precursor compound and the gold precursor compound are applied simultaneously.

  In the method of the present invention, the palladium precursor compound and the gold precursor compound are preferably water-soluble compounds.

  The Pd precursor compound used in the method of the present invention is preferably selected from nitric acid compounds, nitrous acid compounds, acetic acid compounds, tetraamine compounds, diamine compounds, hydrogen carbonate compounds, and metal hydroxide compounds.

An example of a preferred Pd precursor compound is a water-soluble Pd salt. The Pd precursor compound is, in particular, Pd (NH ₃ ) ₄ (HCO ₃ ) ₂ , Pd (NH ₃ ) ₄ (HPO ₄ ), Pd ammonium oxalate, Pd oxalate, K ₂ Pd (oxalic acid) ₂ , Pd (II) trifluoroacetate, Pd (NH ₃ ) ₄ (OH) ₂ , Pd (NO ₃ ) ₂ , H ₂ Pd (OAc) ₂ (OH) ₂ , Pd (NH ₃ ) ₂ (NO ₂ ) ₂ , Pd (NH ₃ ) ₄ (NO ₃ ) ₂ , H ₂ Pd (NO ₂ ) ₄ , Na ₂ Pd (NO ₂ ) ₄ , Pd (OAc) ₂ , and freshly precipitated Pd (OH) ₂ It is preferably selected from the group consisting of

If fresh precipitated Pd (OH) ₂ is used, it is preferably made as follows. Preferably, a 0.1 to 40% by mass aqueous solution prepared from tetrachloropalladium acid.
To this aqueous solution is added a base, preferably an aqueous potassium hydroxide solution, until a brown solid is formed which is a precipitate of Pd (OH) ₂ .
In order to obtain a solution for application on the catalyst support, the newly precipitated Pd (OH) ₂ is isolated, washed and dissolved in an alkaline aqueous solution.
The dissolution is preferably carried out within a range of 4 to 40 ° C, particularly preferably 15 to 25 ° C.
At lower temperatures, it becomes impossible due to the freezing point of water, and at higher temperatures, a precipitate of Pd (OH) ₂ is formed in the solution again after a predetermined time, resulting in inconvenience.

The Pd (NH ₃ ) ₄ (OH) ₂ solution is preferably prepared as follows.
For example, a precursor compound such as Na ₂ PdCl ₄ is made a precipitate of palladium hydroxide using a potassium hydroxide solution, preferably at room temperature and pH 11, as described above, and the precipitate is filtered and filtered. After washing, it is dissolved in an aqueous ammonia solution (up to 8.5%) to obtain Pd (NH ₃ ) ₄ (OH) ₂ (room temperature about 30 minutes, 60 ° C. about 2 hours).

In addition, palladium nitrite precursor compounds can also be used in the process of the present invention. A preferred palladium nitrite precursor compound can be obtained, for example, by dissolving Pd (OAc) ₂ in NaNO ₂ or KNO ₂ solution.

The hydroxo complex or hydroxo compound is particularly preferable as a palladium precursor compound.
As the palladium precursor compound, a Pd (NH ₃ ) ₄ (OH) ₂ compound is particularly preferred.

  The gold precursor compound used in the method of the present invention is preferably selected from acetic acid compounds, nitrous acid or nitric acid compounds, oxidic or hydroxo metal salt compounds.

An example of a preferred gold precursor compound is a water-soluble gold salt. This gold precursor compound includes KAuO ₂ , NaAuO ₂ , LiAuO ₂ , RbAuO ₂ , CsAuO ₂ , Ba (AuO ₂ ) ₂ , NaAu (OAc) ₃ (OH), KAu (NO ₂ ) ₄ , KAu (OAc) ₃ ( OH), LiAu (OAc) ₃ (OH), RbAu (OAc) ₃ (OH), CsAu (OAc) ₃ (OH), HAu (NO ₃ ) ₄ and Au (OAc) ₃ Is preferred.

Au (OAc) ₃ or the above-mentioned gold acid into a new one precipitated as an oxide or hydroxide from a gold acid solution, washed and isolated, and similarly incorporated into acetic acid or alkaline hydroxide It may be appropriate to add one of the salts.

One of the alkali metal salts is particularly preferred for use as a gold-containing precursor compound applied to the support in the form of a solution. The production of potassium oxalate solutions is known from the literature and can be carried out according to the production methods disclosed in WO 99/62632 and US 6,015,769.
Other alkali gold salts can also be obtained in the same manner.
CsAuO ₂ or its hydroxide dissolved in water (CsAu (OH) ₄ ) is particularly suitable for use as a gold precursor compound in the method of the present invention.
In particular, when CsAuO ₂ is used as the gold precursor compound, it does not penetrate deeper into the support than the palladium precursor compound, and can make the two components dispersed and uniform in the shell.

The precursor compound is merely an example here, and other precursor compounds suitable for the production of the VAM shell catalyst can also be used.
Particularly preferred precursor compounds are those that are substantially free of chlorine.
The phrase “substantially free of chlorine” means an empirical rule for compounds not containing chlorine, and does not exclude compounds containing chlorine impurities that cannot be removed, for example, depending on production conditions.

In the step (b), it is particularly preferable that the palladium precursor compound is a Pd (NH ₃ ) ₄ (OH) ₂ compound and the gold precursor compound is CsAuO ₂ .

In step (b) in the method of the present invention, the palladium precursor compound and the gold precursor compound are dissolved in the solution.
The palladium precursor compound and the gold precursor compound can be a mixed solution, but can also be present in separate solutions.
As the pure solvent or the mixed solvent, those in which the selected metal compound is dissolved and can be easily removed from the catalyst carrier after drying are suitable as the solvent for transferring the metal precursor compound.
The solvent is preferably an unsubstituted carboxylic acid, especially a ketone such as acetic acid or acetone, and preferably deionized water.

The precursor compound in step (b) is applied by either a mixed solution containing a gold precursor compound and a palladium precursor compound or two solutions each containing one of the two precursor compounds.
The precursor compound is particularly preferably applied in step (b) to two different solutions simultaneously on the support.

When the gold precursor compound and the palladium precursor compound are applied as a mixed solution, the precursor compound is preferably conveyed from the storage container to the spray nozzle by a pump while the precursor compound is sprayed on the carrier.
When the gold precursor compound and the palladium precursor compound are applied in separate solutions, they are preferably stored in two separate storage containers.
They are then transported by the two pumps to the two spray nozzles, resulting in the two solutions being sprayed separately.
Alternatively, separate solutions may be transported to one spray nozzle by two pumps and both solutions sprayed from one nozzle.

The application of the precursor compound in step (b) of the method of the present invention is preferably carried out by spraying a solution containing the precursor compound onto the carrier.
In particular, it is preferred to move the support with the aid of a support gas (or process gas) during spray coating, for example in a fluidized bed, fluidized bed or Innojet Aircoater, preferably with heated air Is preferred, as a result of which the solvent is quickly evaporated.
In this manner, the precursor compound is present in a defined shell of the support.

The spray rate is preferably a rate that is maintained while the balance between the feed rate of the precursor compound to the carrier and the evaporation rate of the solvent is sprayed.
This can make the shell thickness and the palladium / gold dispersion in the shell desirable.
Depending on the spray rate, the shell thickness can be varied and optimized, for example, to a thickness of 2 mm.
However, very thin shells with thicknesses in the range of 50-300 μm are possible as well.

A spray gas is supplied into the apparatus in which the solution containing the metal precursor compound is sprayed through the spray nozzle, and the gas preferably has non-reducing properties such as air and inert gas. It is preferably supplied at a pressure in the range of 8 bar, more preferably 1.0 to 1.6 bar, most preferably 1.1 to 1.3 bar.
Process air is suitable as a process gas for circulating the carrier.
The pressure and spray rate of the spray gas is selected for the nozzle so that the final droplet of aerosol on the circulating carrier is 1-100 μm, preferably 10-40 μm.
For example, Innojet's “IRN10 PEEK-type Rotojet spray nozzle” can be used here.

The spray rate in the application of the metal precursor compound in step (b) is preferably constant, and the flow rate (of the solution containing the precursor compound) is coated with the precursor compound from 5 g / min to 25 g / 100 g of the carrier to be coated. The ratio is preferably min, more preferably the ratio is 10 g / min to 20 g / min, and particularly preferably the ratio is 13 g / min to 17 g / min.
In other words, the ratio of the weight of the solution to be sprayed with respect to the weight of the packed bed of the carrier is arranged between 0.05 and 0.25, more preferably 0.1 to 0.2, Most preferably, it is 0.13 to 0.17.
When the flow rate or ratio exceeds the above range, it tends to be a catalyst with low selectivity, and when the flow rate or ratio is below the above range, the catalytic action is not adversely affected, but the catalyst production consumes more time. The manufacturing efficiency is reduced.

When a fluidized bed is used as a coating apparatus in the method of the present invention, it is preferable that the carrier circulates in an elliptical shape or a toroidal shape in the fluidized bed.
Conceptually showing how the carrier is moving in the fluidized bed, in the case of elliptical circulation, the carrier in the fluidized bed rides vertically on the elliptical passage while changing the size of the main axis and the second axis. It moves in a plane, and in a horizontal plane, it moves on a circular path while changing its radius.
In general, in the case of “elliptical circulation”, the carrier moves along an elliptical passage in a vertical plane, and in the case of “toroidal circulation”, the carrier moves along a toroidal passage.
This means that the carrier moves in a spiral on a torus surface with an elliptical vertical cross section.

  In the application of the compound in step (b) of the method of the present invention, it is preferred that a so-called controlled air-glide layer is formed in the unit.

  On the one hand, the carriers are well agitated by the controlled air glide layer and at the same time rotate around the axis, they are dried uniformly by the process air.

  On the other hand, the catalyst carrier compact passes through the spraying means (precursor compound application) at a substantially constant speed due to the formation of movement of the support on the orbit influenced by the air glide layer.

In this way, the shell thickness on the treated surface of the carrier or the metal penetration depth into the carrier is made substantially uniform. Throughout the processed batch of compacts, a generally uniform shell thickness is obtained.
As a further result, the concentration of noble metal has changed very slightly over a relatively large region of the shell thickness, in other words, the concentration of noble metal over a relatively large region of the shell thickness generally describes a rectangular function. This ensures that the catalyst has a substantially uniform activity over the thickness of the noble metal shell.

Furthermore, the support used in the method according to the invention is preferably heated during spray coating of the metal precursor compound in step (b), for example by a heated process gas.
The process gas is preferably 10 to 110 ° C, more preferably 40 to 100 ° C, and most preferably 50 to 90 ° C.
The upper limit should be observed to ensure the formation of a thin outer shell with a high concentration of noble metal.

In each case of this application, it is preferable to use air as the process gas.
Nitrogen, CO _2, helium, neon, argon, or mixtures thereof are also available.

  When the palladium precursor compound and the gold precursor compound are applied by a single solution, the solution is preferably in the range of 0.1 to 5% by mass of palladium as the atomic mass ratio of the metal in the solution, More preferably, it contains a palladium precursor compound as described above so that it is contained in the range of 0.3 to 2% by mass, most preferably 0.5 to 1% by mass, and preferably gold is 0.05 to 10% The gold precursor compound as described above is contained so as to be in the range of mass%, more preferably in the range of 0.1 to 5 mass%, and most preferably in the range of 0.1 to 1 mass%.

  When the palladium precursor compound and the gold precursor compound are applied separately by different solutions, the palladium-containing solution preferably has a palladium content of 0.1 to 10% by mass as a proportion of atomic mass in the metal in the solution. Within the range, more preferably within the range of 0.2 to 5% by mass, most preferably 0.5 to 1% by mass, and the gold-containing solution preferably contains 0.1 to 15% by mass of gold. Of these, the content is more preferably in the range of 0.2 to 5 mass%, and most preferably in the range of 0.3 to 1 mass%.

The step after application of the metal precursor compound to the carrier in step (b), the drying step (c), is carried out before the reduction step (d).
This drying step is preferably performed at a temperature lower than the decomposition temperature of the precursor compound, particularly 70 to 120 ° C, more preferably 80 to 110 ° C, and most preferably 90 to 100 ° C.
The drying duration of the carrier to which the metal precursor compound is added is preferably 10 to 100 min, more preferably 30 to 60 min.

This decomposition temperature means the temperature at which the precursor compound starts to decompose.
This drying is preferably carried out using process gas.
When drying is performed in a fluidized bed apparatus or a fluidized bed apparatus, the carrier is preferably allowed to stand in the apparatus, and is preferably not circulated by the process gas.
The drying process in the coating apparatus and not in a separate drying oven has the advantage that no mechanical burden is imposed by the transfer of the support to which the metal precursor compound has been added to further equipment.

This reduces precious metal wear and saves time as well.
In addition, the Applicant has found that there is no penalty for static drying by passing the process gas through the coating apparatus without swirling the support during drying.
The advantages of static drying are low mechanical load and relatively low precious metal loss.

In the step (b) of the method of the present invention, the step of applying the gold precursor compound and the palladium precursor compound at the same time may be carried out by performing preliminary pre-guilding and / or post-post-guilding on the support. You may carry out.
It is preferable that the pre-gilding step or the post-guilding step is carried out in the same manner as the step of applying the precursor compound in the step (b).

Here, it is preferable to use the same compound and the same concentration as in the production of separate solutions containing the gold precursor compound in step (b).
Here, coating by spray coating defined by the simultaneous coating of the metal precursor in step (b) is also preferably performed.
In particular, pre-gilding or post-guilding is preferably spray coated onto the fluidized bed shown above as preferred for step (b) or the carrier fluidized in the fluidized bed.

When performing pre-gilding, the previously specified drying step can be additionally performed thereafter. Further, after preliminary gilding, an intermediate firing step may be performed before the simultaneous application of the metal precursor compound performed in step (b).
Similarly, when post-guilding is performed after application of the metal precursor compound in step (b), a drying or intermediate firing step similar to that defined for pre-gilding may be performed. it can.

When performing pre- and / or post-guilding, it is preferably performed immediately before or after the simultaneous application of the precursor compound in step (b).
In this case, it is particularly preferable that the palladium precursor compound and the gold precursor compound are applied in separate solutions during the simultaneous application in the step (b).

And, for example, start with a spray coating of the gold precursor compound solution for the required pre-guilding and start spraying the palladium precursor compound solution after a predetermined time (while continuing to spray the gold precursor compound solution) Can do.
In a similar manner, post-guilding is also performed by spraying two separate solutions in the application of the metal precursor compound in step (b), and before stopping the spraying of the gold precursor compound solution of the palladium precursor compound. It can be performed by spray coating that finishes spraying.

Pre-gilding has the advantage that during the simultaneous application in step (b) of two precursor compound solutions, these precursor compounds are attached to a carrier already coated with a gold precursor compound.
In particular, as a result of preventing the gold precursor compound solution from penetrating by the carrier as compared with the palladium precursor compound, both metals have a substantially ideal penetration depth in the finished catalyst.
For specific pre-gilding or post-guilding by spray coating, the same spray rate, the same spray rate and the same concentration of gold precursor compound in the solution as the simultaneous application of palladium and gold precursor compound in the method of the present invention Preferably, the spray pressure, the same spray air and the same process gas are applied.

  When performing post-guilding, the step of drying the carrier is not preferred immediately after the simultaneous application of the palladium and gold precursor compound, and in the post-guilding step, the step of additional application of the gold precursor compound The latter is preferred.

If pre-gilding is performed by spray coating in a preferred specific manner prior to the step of simultaneous application of the palladium and gold precursor compound, the spray rate, spray, and spraying of the gold precursor compound when the palladium precursor compound starts spraying The pressure and the concentration of the solution are preferably not changed or changed within a specific range.
The ratio of the time of simultaneous spraying in step (b) of the two metal precursor compound to the spraying time of the gold precursor compound solution in the pre-gilding step is preferably between 8 and 1, and between 6 and 2 More preferably, it is most preferably between 5 and 3.

When post gilding is performed by spray coating, the ratio of the simultaneous spray time in step (b) of the two metal precursor compound to the spray time of the gold precursor compound solution in the post gilding step is between 8 and 1. Preferably between 6 and 2, and most preferably between 5 and 3.
Here again, it is preferable that the concentration, spray rate, and spray pressure of the gold precursor compound solution after the spraying of the palladium precursor compound solution is not changed or changed within a specific range.

Spraying the solution containing the precursor compound is effective at all steps in the method of the present invention, and it is preferable to spray the solution with the aid of a spray nozzle.
Here, the annular gap nozzle is preferably used for spraying mist as a plane that is symmetrical to a preferred plane parallel to the apparatus base.
Since it can be sprayed around 360 degrees, the molded body falling to the center can be sprayed evenly, especially with the solution.
The annular gap nozzle is preferably completely embedded in the device in which the orifice is circulated.

According to a preferred embodiment of the present invention, the annular gap nozzle is arranged at the center of the base of the device in which the circulating movement of the carrier is carried out, and the orifice of the annular gap nozzle is completely embedded in the device.
As a result, the free path for the fog particles to meet the compact can be made relatively short, so that large droplets that act in reverse to make the shell thickness generally homogeneous are There will be little time left by the fusion.

The reduction of the metal precursor compound to metal in step (d) is likewise carried out in the coating apparatus.
Similarly, the advantage is achieved that the coated carrier is not exposed to mechanical loads that cause metal loss.

During the step of performing the reduction of the metal component, the support is preferably not moved and is allowed to stand in the coating apparatus.
By this method, metal loss can be greatly reduced.

This reduction step is preferably performed by temperature treatment in a non-oxidizing atmosphere in order to reduce the metal component of the precursor compound to a metal.
The temperature treatment in this non-oxidizing atmosphere is preferably performed in a temperature range of 40 to 400 ° C, more preferably 50 to 200 ° C, and most preferably 60 to 150 ° C.

In the present invention, the non-oxidizing atmosphere means an atmosphere containing no or almost no oxygen or other gas having an oxidizing action.
The non-oxidizing atmosphere can be an inert gas atmosphere or a reducing atmosphere.
The reducing atmosphere may be formed by a gas having a reducing action or a mixed gas of a gas having a reducing action and an inert gas.

As a modification of the method of the present invention, the reduction can be carried out in an inert gas atmosphere.
In this case, the metal counter ion of the metal-containing precursor compound has a reducing action.
Counterions having a reducing action in such cases are well known to those skilled in the art.

  Furthermore, as a modification of the present invention, the temperature treatment can be performed directly in a reducing atmosphere. In this case, the precursor compound is decomposed at the same temperature as the temperature treatment, and the metal component is reduced to the metal.

Furthermore, in another modification of the present invention, the temperature treatment can be preferably performed in such a manner that the inert gas atmosphere is changed to the reducing atmosphere during the temperature treatment.
The precursor compound is first decomposed at the decomposition temperature in an inert gas atmosphere, and the metal component is reduced to a metal by changing to a reducing atmosphere.
The decomposition temperature under an inert gas is set to 200 to 400 ° C.
The temperature of the subsequent reduction is the temperature specified above.

  According to the present invention, it is preferable to switch from an inert gas atmosphere to a reducing atmosphere so that a temperature drop below a temperature suitable for reduction does not occur during switching.

N ₂ , He, Ne, Ar, or a mixture thereof is used as the inert gas, for example.
N ₂ is particularly preferably used.

The component having a reducing action in a reducing atmosphere is usually selected based on the characteristics of the metal component to be reduced, and is preferably ethylene, hydrogen, CO, NH ₃ , formaldehyde, methanol, formic acid, hydrocarbons, or these It is composed of a vaporizable liquid or gas such as a mixture of two or more of gas and liquid.
The reducing atmosphere particularly preferably contains hydrogen as a reducing component.
In particular, when the reducing atmosphere is formed by a gas, a mixture of N ₂ and H ₂ is preferable.
The hydrogen content is in the range of 1% to 15% by volume. The reduction in the present invention is performed, for example, in a process gas containing hydrogen (4 to 5% by volume) in nitrogen at a temperature range of 60 to 150 ° C., for example, 0.25 to 10 hours, preferably 2 to 6 hours. It can be done throughout the period.

In the second method of changing from an inert gas to a reducing atmosphere in the reduction step, instead, the reducing component may be supplied into the inert gas atmosphere.
Hydrogen gas is preferably supplied.
The supply of the reducing gas to the inert gas has the advantage that it does not cause a significant or lower temperature drop to or below 60 ° C., the lower limit of the desired temperature for the reduction. As the total atmosphere changes, there is no need to separately concentrate energy and costs for heating.

  The catalyst support obtained after the reduction is preferably 0.5 to 2.5% by mass of palladium, more preferably 0.7 to 2% by mass, and still more preferably 0.9% with respect to the total mass of the catalyst support. It is contained at a ratio of ˜1.5% by mass.

  The catalyst support obtained after the reduction is preferably 0.1 to 1.0% by mass of gold, more preferably 0.2 to 0.8% by mass, and still more preferably 0 to the total mass of the catalyst support. .3 to 0.6% by mass.

  According to the method of the present invention, it is particularly preferable that all optional steps such as pre- and post-guilding and drying are performed in the coating apparatus before the step (e) of removing the carrier from the coating apparatus.

During steps (a) to (e) in the method of the present invention, the support preferably remains in the coating apparatus, and is preferably removed from the apparatus and not reintroduced for any intermediate processing. .
By performing all the steps in one apparatus, time (ie, cost) savings are realized in the production of VAM catalysts compared to conventional production methods. Furthermore, metal wear is also kept within an acceptable range. Compared to the conventional manufacturing method with a metal yield of 94% at maximum, according to the manufacturing method of the present invention, the metal yield can be increased to 97%.
This is particularly difficult to predict from the mechanical loading of the carrier that occurs during movement in the fluidized bed.

In order to produce a catalyst by the method of the present invention, it is preferable to apply an alkali acetate to the support.
The application of the alkali acetate is performed in principle before the step (a), but may be performed after the step (e) or between the steps (a) to (e).
In the present invention, it is particularly preferable that the application of the alkali acetate is performed before the application of the metal precursor compound in order to minimize the loss of the noble metal due to the mechanical load on the support after the application of the metal precursor compound. .
The step of applying the alkali acetate is preferably carried out before the step (a) of the present invention.

After applying the alkali acetate, it is preferable to perform the drying step by allowing the carrier to stand in the apparatus without being circulated by the process gas.
The drying conditions are shown below.

  Contrary to the view that has been kept so far regarding the production of VAM catalysts, the applicant of the present application applies alkaline acetate to the support before application of the metal precursor compound and before reduction of the metal component of the precursor compound. Surprisingly leads to an improvement in the activity and selectivity of the VAM catalyst over the shell catalyst coated with alkali acetate after application of the metal precursor compound and / or after reduction of the metal component of the precursor compound. I made a discovery.

  As the alkali acetate, lithium acetate, sodium acetate, potassium acetate, cesium acetate, and rubidium acetate can be used, and potassium acetate is preferable.

In order to apply alkali acetate in the present invention, a solution containing alkali acetate is preferably prepared.
Water is preferably used, more preferably deionized water as the solvent for the solution. The concentration of the alkali acetate in the solution is preferably 0.5 to 5 mol / L, more preferably 1 to 3 mol / L, still more preferably 1.5 to 2.5 mol / L, and most preferably 2 mol / L. L.

  The application of the solution containing the alkali acetate can be carried out by any method. This application can be carried out by a pore filling method known in this technical field (incipient wetness method) or other methods, and in the present invention, before the step (a), Preferably, it is applied.

Alternatively, the carrier can be coated with alkali acetate by spray coating.
The carrier may be stationary but is preferably moved.
For the movement of the carrier, all possible ways can be taken, for example a coating drum, a mixing drum or a method with the aid of a support gas. The movement of the support during spray coating is preferably carried out with the aid of a support gas (or process gas), for example in a fluidized bed, fluidized bed or Innojet AirCoater, with heated air being blown. It is preferable to add, and as a result, evaporation of the solvent is quick.
Here, the temperature is preferably 15 to 80 ° C, more preferably 20 to 40 ° C, and most preferably 30 to 40 ° C.

  If alkali acetate spray coating is performed prior to coating with a metal precursor compound, the advantage is that a torus-shaped alkali-containing structure is formed in the volume of the support, where the precious metal is retained later. Almost no alkali is present on the surface of the carrier, so that the precious metal is absorbed in the second coating.

When the alkali acetate is applied by spray coating, the spray rate is preferably a rate that is maintained while the balance between the supply rate of the precursor compound to the carrier and the evaporation rate of the solvent is sprayed.
During spraying of the solution containing alkali acetate, the spray rate is preferably constant, and the flow rate is preferably 5 g / min to 25 g (solution) / min per 100 g of the carrier to be coated, more preferably The ratio is 10 g / min to 20 g / min, and particularly preferably this ratio is 13 g / min to 17 g / min.

  The solution containing the alkali acetate is preferably sprayed into the apparatus through a spray nozzle, where a spray gas is supplied, which is preferably air, and has a pressure in the range of 1 to 1.8 bar. Preferably from 1.0 to 1.6 bar, and most preferably from 1.1 to 1.3 bar. Process air is suitable as a process gas for circulating the carrier.

  The spray rate and the pressure of the spray gas are selected for the nozzle so that the final droplet of aerosol on the circulating carrier is 1-100 μm, preferably 10-40 μm. For example, Innojet's “IRN10 PEEK-type Rotojet spray nozzle” can be used here.

  The addition of alkali metal is preferably 2 to 3.5% by mass, more preferably 2.2 to 3.0% by mass, based on the total mass of the carrier dried after coating, Most preferably, it is -2.7 mass%.

After application of the solution containing alkali acetate, preferably in the temperature range of 70-120 ° C, more preferably in the range of 80-110 ° C, most preferably in the range of 90-100 ° C, air, dilute Drying in air or inert gas is preferably carried out.
The drying period of the carrier to which the alkali metal has been added is preferably 10 to 100 min, more preferably 30 to 60 min. Drying of the support to which the alkali metal has been added can also be carried out in the coating apparatus. Drying is preferably carried out with the carrier standing, and without movement.
For example, if a fluidized bed or fluidized bed apparatus is used, it is preferable not to move the carrier during drying in the fluidized bed or fluidized bed apparatus.

In one embodiment of the present invention, it is preferable that the carrier is coated with an alkali acetate by a pore filling method before the step (a). The carrier is then introduced into the coating apparatus.
The carriers are preferably kept swirled to remove dust from them with the aid of process air as support gas in the fluidized bed or fluidized bed.
Pre-gilding by spraying the solution containing the gold precursor compound onto the fluidized carrier is preferably initiated at about 70 ° C.

When the temperature reaches about 80 ° C., switch to either a spray of the mixed solution or a spray of two solutions containing the palladium precursor compound and the gold precursor compound.
Immediately thereafter, post-guilding is carried out by spraying a solution containing the gold precursor compound at the same temperature.
In the coating apparatus, the temperature is raised to 85-100 ° C. and the support is preferably dried statically.
Following one of the steps defined above, the reduction is preferably carried out while the carrier is left stationary with the forming gas.

  A further object of the present invention is a shell catalyst obtainable by the invention. The shell catalyst according to the present invention has very high selectivity and activity in the synthesis of VAM, unlike conventional catalysts for the synthesis of VAM.

This exhibits the property that metal wear is reduced during manufacture according to the present invention, which results in not only high metal addition, but also reduced pore blockage due to dust generated by wear.
In the excellent selectivity and activity of the shell catalyst of the present invention, the difference that clearly exists between the conventional catalyst and the conventional catalyst cannot be expressed by physical values at the time of this application. The shell catalyst according to the present invention is distinguished from the conventional catalyst in its production method and achievement of selectivity and activity.

Other embodiments relate to the use of shell catalysts prepared using the process of the present invention for the preparation of carboxylic acid alkenyl esters, particularly VAM and allyl acetate monomers.
In other words, the present invention relates to a process for producing VAM or allyl acetate in which acetic acid, ethylene or propylene and oxygen or an oxygen-containing gas are passed through the catalyst of the present invention.

In general, this is acetic acid, ethylene and oxygen or an oxygen-containing gas over the catalyst of the invention at a temperature of 100 to 200 ° C., preferably 120 to 200 ° C. and 1 to 25 bar, preferably 1 to 20 bar. Is carried out by passing through, where the non-reacted extract can be recycled.
For convenience, the oxygen concentration is kept below 10% by weight.
However, under certain circumstances, diluting with an inert gas such as nitrogen or carbon dioxide is also useful.

Carbon dioxide is formed in small amounts in the VAM synthesis process and is particularly suitable for dilution and is collected in the recycle gas.
The formed vinyl acetate is isolated with the aid of a suitable method, for example as described in US 5,066,365A. A similar method has been published for allyl acetate.

  The present invention is further described in detail below with reference to the drawings and embodiments, but is not to be construed as being limited thereto.

FIG. 1 shows the amount of VAM molecules per molecule of oxygen as a function of CO ₂ / O ₂ ratio when the shell catalyst of the present invention and two comparative catalysts are used in the catalytic synthesis of VAM. . FIG. 2 shows the space-time yield (STY) of VAM as a function of O ₂ conversion when the shell catalyst of the present invention and two comparative catalysts are used in the catalytic synthesis of VAM.

Example 1: Production of catalyst A

First, 100 g of the carrier “KA-Zr-14” (including 14% ZrO ₂ -doped KA-160 carrier, manufactured by Zude Chemie) was baked at 750 ° C. for 4 hours. The carrier was then sent to an Innojet Air-Coater 025-type fluidized bed where dust was removed for 10 minutes using air as the process gas.
Thereafter, 20.32 g of a 2 molar KOAc solution was sprayed onto a rotating carrier at 33 ° C. with a spray rate of 15 g / min / 100 g carrier.
The carrier was then allowed to stand and dried at 88 ° C. for 35 minutes. After drying, a new flow of the support was performed again with the aid of air as process gas.
First, an aqueous solution containing KAuO ₂ (prepared by mixing 3.6% Au solution 4.05 g + 50 mL water) is placed on a rotating carrier at 70 ° C., spray rate 15 g (solution) / min. Sprayed with / 100 g carrier.
Then, directly, two solutions are sprayed in parallel, where one solution is an aqueous solution containing KAuO ₂ (prepared by mixing 3.6% Au solution 4.05 g + 50 mL water). The other solution contains Pd (NH ₃ ) ₄ (OH) ₂ (prepared by mixing 32.58 g of 4.7% Pd solution + 50 mL of water).
Both solutions were sprayed at a temperature of 70 ° C. with a spray rate of about 15 g (solution) / min / 100 g carrier.
Then, an aqueous solution containing KAuO ₂ (produced by mixing 3.6% Au solution 4.05 g + 50 mL water) was sprayed at 15 g (solution) / min / 100 g carrier at 70 ° C. Sprayed at temperature.
Thereafter, the carrier was left in the coater again, and dried in this state at 90 ° C. for 35 minutes.
The support was then reduced with forming gas (98% N ₂ and 2% H ₂ ) at 700 ° C. for 25 minutes.

According to ICP-AES analysis, in each case relative to the total mass of the support, the palladium ratio was 1.4% by mass and the gold ratio was 0.4% by mass.
The yield of precious metals of palladium and gold was 97% with respect to the amount used.

Comparative Example 1 Production of catalyst B

First, 100 g of the carrier “KA-Zr-14” (including 14% ZrO ₂ -doped KA-160 carrier, manufactured by Zude Chemie) was baked at 750 ° C. for 4 hours. The carrier was then sent to an Innojet Air-Coater 025-type fluidized bed where dust was removed for 10 minutes using air as the process gas.
First, an aqueous solution containing KAuO ₂ (prepared by mixing 3.6% Au solution 4.05 g + 50 mL water) is placed on a rotating carrier at 70 ° C., spray rate 15 g (solution) / min. Sprayed with / 100 g carrier.
Directly, two solutions are then sprayed in parallel, where one solution is an aqueous solution containing KAuO ₂ (prepared by mixing 3.6% Au solution 4.05 g + 50 mL water). The other solution contains Pd (NH ₃ ) ₄ (OH) ₂ (prepared by mixing 32.58 g of 4.7% Pd solution + 50 mL of water). Both solutions were sprayed at a temperature of 70 ° C. with a spray rate of about 15 g (solution) / min / 100 g carrier.
Then, an aqueous solution containing KAuO ₂ (produced by mixing 3.6% Au solution 4.05 g + 50 mL water) was sprayed at 15 g (solution) / min / 100 g carrier at 70 ° C. Sprayed at temperature.
Thereafter, the carrier was left in the coater again, and dried in this state at 90 ° C. for 35 minutes.
The carrier was then removed from the coater and transferred to a reduction furnace where it was reduced with H _{2 at} 150 ° C. for 4 hours.
The support was then impregnated with KOAc by applying a 2 molar KOAc solution to it by the incipient wetness method.

According to ICP-AES analysis, in each case relative to the total mass of the support, the palladium ratio was 1.4% by mass and the gold ratio was 0.4% by mass.
The yield of precious metals of palladium and gold was 94% with respect to the amount used.

Comparative Example 2: Production of catalyst C

31.38 g of Pd (NH ₃ ) ₄ (OH) ₂ solution (4.7%) and 10.89 g of KAuO ₂ solution (3.6%) were diluted with 50 mL of distilled water and mixed solution As a spray rate 15 g / min / 100 g carrier, applied to KA-16 carrier at a temperature of 70 ° C. (available from Sud Chemie AG).
The support was swirled by air as process gas in an Air-Coater 025-type from Innojet.
The obtained carrier was dried at 90 ° C. for 45 minutes in a stationary state in a coater.
The sample was then reduced at 150 ° C. for 4 hours in another reduction reactor using forming gas (3% by volume H ₂ in N ₂ ). After reduction, the catalyst was impregnated with a KOAc solution (1.95 g of 2 molar KOAc solution and 3.99 g of distilled water) by the incipient wetness method.
Thereafter, the sample was dried at 90 ° C. for 45 minutes in a stationary state in a fluidized bed drying apparatus.

According to ICP-AES analysis, in each case relative to the total mass of the support, the palladium ratio was 1.4% by mass and the gold ratio was 0.4% by mass.
The precious metal yield of palladium and gold was 92% with respect to the amount used.

Comparative Example 3: Production of a catalyst according to WO2008 / 145393

The catalyst was prepared according to the examples of WO2008 / 145393. The average yield of noble metal was 88% for palladium and 85% for gold.

Example 2: Test results on the activity and selectivity of each of catalysts A to C in the synthesis of VAM

For this purpose, acetic acid, ethylene and oxygen pass the catalysts A and B, respectively, at a pressure of 6 bar, temperature 140 ° C./12 hours → 142 ° C./12 hours → 144 ° C./12 hours → 146 ° C./12 hours ( Each reaction temperature was applied based on a sequence during the automatic execution of the screening method.
That is, the measurement is performed at a reaction temperature of 140 ° C. for 12 hours, then 144 ° C. for 12 hours, then 144 ° C. for 12 hours, and then 146 ° C. for 12 hours). Concentrations of components were 38% for ethylene, 5% for O ₂ , 0.9% for CO ₂ , 9% for methane, 12% for acetic acid, and N ₂ for the rest.

1 and 2 show the selectivity or activity of catalysts A, B and C as an O ₂ conversion function. The values are also shown in Tables 1, 2 and 3 below.

  As can be seen from the comparison of Tables 1 to 3 and FIGS. 1 and 2, the catalyst A produced by the present invention has extremely high selectivity and activity (oxygen conversion rate) compared to the catalysts B and C.

Claims (16)

The method for manufacturing a shell catalyst which has the following process.
(A) introducing a carrier into the coating apparatus;
(B) In the coating apparatus, a palladium precursor compound and a gold precursor compound are applied to the carrier by spray coating in a solution state, respectively.
(C) drying the carrier coated with the precursor compound in the coating device, wherein the carrier is allowed to stand in the coating device during the drying; (d) in the coating device; Reducing the metal component of the precursor compound to metal, and
(E) Remove the carrier from the coating apparatus.   The method of claim 1, wherein the palladium precursor compound is a hydroxo complex.   The method according to claim 1 or 2, wherein the gold precursor compound is a gold salt.   4. The method according to claim 1, wherein in the step (b), the coating is performed simultaneously with the application of the palladium precursor compound and the gold precursor compound. 5.   In the step (b), the application of the palladium precursor compound and the application of the gold precursor compound are performed by spray coating with a mixed solution containing both precursor compounds, or spraying two solutions each containing one of the precursor compounds. The method according to claim 1, wherein the method is carried out by coating.   6. The method according to any one of claims 1 to 5, wherein a further application of a gold precursor compound is carried out on the support between step (a) and step (b).   7. The method according to any one of claims 1 to 6, wherein a further application of a gold precursor compound is carried out on the support between step (b) and step (c).   The method according to claim 6 or 7, wherein the gold precursor compound is applied by spray coating of a solution containing the precursor compound.   9. A method according to any one of the preceding claims, wherein the carrier is swirled in the glide layer with process gas during spray coating.   The method according to any one of claims 1 to 9, wherein the apparatus is a fluidized bed apparatus or a fluidized bed unit.   The method according to any one of claims 1 to 10, wherein after step (a), before spray coating of the metal precursor compound, the step of removing dust by swirling the carrier in the glide layer by the process gas is performed. . The method according to any one of claims 1 to 11 to implement the reduction of the metal component in a non-oxidizing atmosphere. The method according to claim 12 , wherein the non- oxidizing atmosphere includes hydrogen gas or ethylene as a reducing agent. The method according to any one of claims 1 to 13 , wherein the carrier is allowed to stand in the coating apparatus during the reduction step (d). Claims 1 to 14 either way shell catalyst for synthesis of carboxylic acid alkenyl esters obtained by utilizing the. Use of the shell catalyst according to claim 15 or the shell catalyst prepared according to any one of claims 1 to 14 for the production of carboxylic acid alkenyl esters.